Electromagnetic based instruments for measuring properties of matter or identifying its composition are well known. Magnetic resonance spectroscopy is one of the principal measuring techniques used to obtain physical, chemical and structural information about a molecule. In order to be able to perform magnetic resonance spectroscopy with high resolution capabilities providing a high quality image (i.e., resolution and contrast) the magnetic field used must be extremely stable and uniform.
However in order to achieve such uniformity, elements correcting the inhomogeneousness of the main magnetic field are added, according to the principle of fields' superposition. Coils, magnetic parts, or all other means enabling correction of the imperfections of the principal field are added in order to obtain a homogeneous total field in the zone of interest.
U.S. Pat. No. 5,959,454 to Westphal et al. discloses a magnet arrangement for an NMR tomography system, in particular for skin and surface examinations, which contains a one sided NMR system having two ring magnets and a cylindrical magnet. Their respective locations provide a certain degree of uniformity.
U.S. Pat. No. 6,191,584 presents a permanent magnet for NMR image detection which contains a magnetic structure having a yoke and magnetic poles, so shaped as to delimit or enclose a cavity.
In order to achieve a uniform and strong magnetic field using permanent magnet material, the use of simple permanent magnet structures, like C-magnet or H-magnet, is not suitable. Therefore, much more complex assemblies are needed in order to achieve the required magnetic field. Modern magnetic material today can hold high magnetic energy, and if a magnetic circuit is designed correctly, uniformity and field strength can be achieved and controlled with high efficiency. A cost-effective self-fastening cage useful for providing a homogeneous, stable and uniform magnetic field, thus still meets a long felt need.